to clarify... you want to plant a tree... and then have little trees growing on that tree? what would the little trees take root in? a planter box? please explain...

most of the time for planting you just need to ensure a certain depth of soil depending on the type and size of the plant.

god i hope you mean trees on a roof and not trees on trees...

The most important thing in building a planted roof or just a green roof is the protection of the structure, the water drainage and the insulation.
Usually the soil depth for a non intensive green roof is about 4-6 inches, for an intensive green roof it's about 24 inches or more.

Tenax
Green Roof Tops

sorry my mistake. I meant a ron a roofoof, not a tree... I got distracted. But thanks for the info. I can look more into depth right now.

Ron, a "roofoof."

usually you need about 800mm minimum to grow a "tree". but for grass my boss got the depth down to 50mm on his house.

Some trees will grow anywhere- more important is how big do you want this prisoner to grow? if all you want is a spindly shrub or whip then a few cubic feet in a container will suffice. for a honking big ass monster then the more soil the better! 800 cu feet soil each planting pit for street trees was a prof's advice.

Think volume, not depth- check out species that thrive on rock outcroppings or above hardpan- they don't need much soil or depth...

Also remember aeration/ventilation for healthy roots and roof deck- the best reason to use a plastic eggcrate is for air circulation, not drainage or water storage- that's what the soil is for.

I'll bet this prisoner doesn't have 800 cu ft!!



Thanks to snjr for alerting me to the Greensburg, Indiana tree-on-a-roof (aka roofoof) (sorry).

hahahahahahahahahah

Don't forget - in every square foot for every 6 inches deep of soil, that's 100 pounds of soil plus 100 pounds of water. In addition, you've got to remember to calculate the load based on the mature weight of the tree, not the initial weight. Stupid growing things...

Metric huh? Don't ask me about that yet, the US goes metric in 1995, so I've still got 11 years to get it down.

Wax- great pic.

Crowbert, you're an architect, not a 'scaper, leave this to the experts. A cubic foot of h2o is 62 lbs - not 100#. For roofs & such, we typically spec a lightweight planting mix - 100lbs/cf is a generic figure to use, but we can reduce this by using expanded shale or perlite.... Hire a soils expert or a local LA with lots of plants-on-structures experience. You match the soil to the plants, not to the building...

Weight of the trees is a point load and not a typically a limiting factor - just place them over the columns. More critical is that they have sufficient soil area so they don't blow over - roofs are windy. The live load is more significant over the entire roof- discuss this with your structural engineer.